GSFC: TESS Delivers New Insights into an Ultrahot World

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bystander
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GSFC: TESS Delivers New Insights into an Ultrahot World

Post by bystander » Tue Jun 30, 2020 5:51 pm

TESS Delivers New Insights into an Ultrahot World
NASA | GSFC | TESS | 2020 Jun 30
Click to play embedded YouTube video.
Explore KELT-9 b, one of the hottest planets known. Observations from NASA's Transiting
Exoplanet Survey Satellite (TESS) have revealed new details about the planet’s environment.
The planet follows a close, polar orbit around a squashed star with different surface
temperatures, factors that make peculiar seasons for KELT-9 b. Credit: NASA/GSFC/SVS

Measurements from NASA’s Transiting Exoplanet Survey Satellite (TESS) have enabled astronomers to greatly improve their understanding of the bizarre environment of KELT-9 b, one of the hottest planets known.

“The weirdness factor is high with KELT-9 b,” said John Ahlers, an astronomer at Universities Space Research Association in Columbia, Maryland, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s a giant planet in a very close, nearly polar orbit around a rapidly rotating star, and these features complicate our ability to understand the star and its effects on the planet.” ...

Located about 670 light-years away in the constellation Cygnus, KELT-9 b was discovered in 2017 because the planet passed in front of its star for a part of each orbit, an event called a transit. Transits regularly dim the star’s light by a small but detectable amount. The transits of KELT-9 b were first observed by the KELT transit survey, a project that collected observations from two robotic telescopes located in Arizona and South Africa. ...

KELT-9 b is a gas giant world about 1.8 times bigger than Jupiter, with 2.9 times its mass. Tidal forces have locked its rotation so the same side always faces its star. The planet swings around its star in just 36 hours on an orbit that carries it almost directly above both of the star’s poles.

KELT-9 b receives 44,000 times more energy from its star than Earth does from the Sun. This makes the planet’s dayside temperature around 7,800 degrees Fahrenheit (4,300 C), hotter than the surfaces of some stars. This intense heating also causes the planet’s atmosphere to stream away into space. ...

KELT-9 b’s Asymmetric TESS Transit Caused by Rapid Stellar
Rotation and Spin-Orbit Misalignment
~ John P. Ahlers et al
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Re: GSFC: TESS Delivers New Insights into an Ultrahot World

Post by Ann » Wed Jul 01, 2020 8:27 pm

Francis Reddy of NASA’s Goddard Space Flight Center wrote:

Its host star is an oddity, too. It’s about twice the size of the Sun and averages about 56 percent hotter. But it spins 38 times faster than the Sun, completing a full rotation in just 16 hours. Its rapid spin distorts the star’s shape, flattening it at the poles and widening its midsection. This causes the star’s poles to heat up and brighten while its equatorial region cools and dims — a phenomenon called gravity darkening. The result is a temperature difference across the star’s surface of almost 1,500 F (800 C).















So the host star of KELT-9 b is somewhat similar to Altair!
Francis Reddy wrote:

This illustration shows how planet KELT-9 b sees its host star. Over the course of a single orbit, the planet twice experiences cycles of heating and cooling caused by the star’s unusual pattern of surface temperatures. Between the star’s hot poles and cool equator, temperatures vary by about 1,500 F (800 C). This produces a “summer” when the planet faces a pole and a “winter” when it faces the cooler midsection. So every 36 hours, KELT-9 b experiences two summers and two winters.
Wow! :shock:

Ann

Edit: I was so lazy that I didn't check out the video on KELT-9 b before I made my post. The video said that the temperature of host star KELT-9 is 9,930 oC (9657 K?). That makes KELT-9 similar to Vega (9602 K) in temperature, not similar to Altair or Deneb.
Last edited by Ann on Thu Jul 02, 2020 5:36 am, edited 2 times in total.
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Re: GSFC: TESS Delivers New Insights into an Ultrahot World

Post by neufer » Wed Jul 01, 2020 10:08 pm

Assuming that KELT-9 b doesn't pass directly over the poles it must precess like crazy :derp: .

How long before it no longer transits :?:
Art Neuendorffer

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